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Abstract. Both low temperature and light energy are important reasons for the decline in cucumber yield in winter of east and north China, therefore optimal utilization of light energy is critical for raising cucumber yield. In this study, Three-Dimensional (3D) cucumber canopy models were used to quantify the effects of weak light on dry matter production. Three 3D cucumber canopies were reconstructed with 20, 25, 30 leaves per plant respectively by using parametric modeling method. Light interception in these three 3D canopies from 8:00 to 15:00 on 4 Nov, 2015 was simulated by using the Radiosity-Graphic combined Model (RGM) with an hourly time step. CO₂ assimilation per unit area was calculated using the FvCB photosynthetic model. As a result, the effects of light intensity and CO₂ concentration on the photosynthetic rate were considered. The leaf photosynthesis simulation result showed that during the daytime in winter, the limiting factor affecting the photosynthesis rate in winter was light intensity. Especially in the morning, the CO₂ concentration in the greenhouse was significantly higher than other moments. Increasing the light intensity or canopy light interception at this time should be very beneficial to the increase in yield production. It could be concluded that 25-leaf canopy was a more suitable canopy structure to autumn and winter canopy photosynthetic yields, through the comparative analysis of photosynthetic characteristics in these three virtual 3D canopies. This study also provides an important management basis for the optimal use of light in the greenhouse in winter of east China.